Joining or splicing of optical fibers to optical fibers or optical waveguides on bulk material is of major importance in most fiber optics devices. The most common technology for fiber joining is fusion splicing, using an electrical arc short pulse for heating the two fiber ends while being spliced. This technology is applicable to fibers of equal diameters, but is not applicable for fiber to optical waveguides or bulk material attachment, since the bulk dimensions are much larger than the fiber and arc splicing cannot heat both the fiber and the optical waveguides or bulk material attachment equally and get an equal layer melted on both surfaces of the optical splice.
There are a number of known technologies for coupling or bonding a silica optical fiber to optical waveguides on bulk. Epoxy adhesive or simply epoxy is the predominant current bonding technology. The epoxy is introduced between the fiber and appropriate optical waveguides port and cured with the help of UV radiation. Epoxy serves not only as a bonding material; it enables some refractive index matching reducing transmission losses. Although simple, the method suffers of a number of shortcomings: Curing of the epoxy is not uniform; epoxy curing time is relatively long and the fiber frequently changes its position after alignment; epoxy out gassing adversely affects the hermetic photonic element packaging, and the optical transmission of the epoxy changes with the time. Since light passes through the epoxy, high power applications are prohibited. This procedure of splicing is a multi-step process, requiring a relatively long time. Some temporary splices use index-matching gel between the two surfaces, and need a permanent mechanical set up for aligning.
U.S. Pat. No. 6,296,401. to Paris and U.S. Pat. No. 6,411,759. to Beguin et al., disclose methods of optical fiber to waveguide connection by fusion. Paris shows a method for fusion pigtailing of an optical fiber to an integrated optical device with an optical device formed on a substrate. The substrate includes a groove under and behind an interface between the optical fiber and the optical device. Provision of such a groove allows the substrate to be used for alignment and support of the optical fiber, while reducing optical insertion loss and improving durability of the interface. Paris does not disclose the method according to which fiber fusion is performed.
Beguin shows a fusion joint between a waveguide and an optical fiber created by irradiating the interface between the optical fiber and the waveguide using a laser beam. The spatial distribution of the energy furnished to the interface presents a central zone of which the energy is reduced with respect to a peripheral zone, whereby to enable a relatively high-energy laser to be used while avoiding bending of the waveguide by high power laser heating. The laser beam is caused to irradiate a higher energy density upon the waveguide than the optical fiber, typically by offsetting the center of the laser beam towards the waveguide. The fusion is performed by the heat generated by the laser light absorption, while a force F urges the waveguide and optical fiber towards one another, to avoid the creation of a void at the boundary. Beguin irradiates a relatively large area that includes both the waveguide and the fiber. This causes some waste of laser energy, the heating process is not a homogenous one, the fusion process take excessive time and because of the waveguide heating requires additional annealing steps.
U.S. Pat. No. 6,360,039. to Bernard et al. discloses a method of joining at least two optical components. One of the optical components having a surface that has a comparatively larger cross-sectional area than the surface of the other optical component e.g. an optical fiber. The optical components are joined together by fusion-splicing, using a laser for heating. The fusion is achieved by melting a small area surrounding the joint with the fiber section on the larger than the optical fiber component by a process where the larger surface is first pre-heated by the laser. The pre-heat temperature is just sufficient to polish and melt the surface of the larger component at the location one desires to fuse the smaller component. The second surface is then brought into contact with the preheated surface and, once the thermal exchange is established (by conduction of heat), all components are heated simultaneously. This process requires a long time and needs customization for each geometry.
U.S. Pat. Application No. 20050180695. to Bronstein et al. discloses a method of joining a fiber and waveguide using a laser through the fiber, where the fiber is coated with laser absorbing glass powder or a special laser absorbing dye. Realization of this method is very problematic since the splice contains many laser absorbing centers, remnants of the initial absorbers, the splice has very high insertion loss and high reflections making it unfit for optical communication.
The need for an “instant” splicing, mainly of fibers to bulk materials or to waveguides in bulk material, calls for novel methods for attachment. This invention provides such a novel method.